In the processing of tubular knitted fabrics, it is frequently necessary or desirable to pass the fabric tube over a spreader frame, which serves to distend the fabric laterally into flat, two-layered form, of predetermined width. Frequently, the fabric is in wet condition and/or is subjected to steam while on the spreader, and the fabric is then discharged from the spreader directly into a subsequent processing machine, such as a calender, compressive shrinkage station, padding or dyeing machine or the like.
Inasmuch as the spreader frame is necessarily received internally of the tubular fabric, and the fabric may be continuous in nature, the spreader frame is required to be supported externally of the fabric tube. In one particularly advantageous form of the fabric spreader frame, the frame is supported by means of power driven edge drive rolls, which engage pairs of idler rolls mounted on the spreader frame itself. Since a layer of fabric is, of course, interposed between the edge drive rolls and the idler support rolls of the frame, relatively light pressure contact is maintained on the spreader frame to avoid marking or damaging the fabric. Moreover, since the entire weight of the spreader frame is supported on the edge drive rolls, the construction of the spreader frame is maintained as lightweight as is reasonably practicable under the service conditions. Accordingly, in a typical commercial installation, the supporting and driving of the spreader frame is a relatively sensitive, delicate structural arrangement. Whenever there is an effective discontinuity in the free flow of tubular fabric onto the upstream or entry end of the spreader frame, such as when the fabric becomes tightly twisted, or the entry end of the spreader penetrates a large tear in the fabric, for example, the forward tension on the fabric may dislodge the spreader frame from its mountings and tend to drag it forward into the processing apparatus. This is, of course, a well known problem, and many mechanical and electrical arrangements have been proposed and provided for the purpose of effecting stoppage of the equipment whenever such dislodgement occurs, to minimize or prevent damage. Advantageous examples of such arrangements are shown in, for example, the earlier Rockman, et al. U.S. Pat. Nos. 3,797,080 and 3,893,213, granted to Samcoe Holding Corp. The mechanisms of the Rockman et al patents provide for limited yieldable mounting of at least one of the edge drive rolls, in conjunction with means for sensing transverse movement of the edge drive roll as results from a dislodgement of the spreader frame.
The system of the present invention has for its ultimate purpose the sensing of any dislodgement of the spreader frame and the stoppage of the equipment as a function thereof. In this sense, the intended function of the system is the same as that of earlier systems. However, the system of the present invention is improved and simplified in significant respect. First, the system provides for mounting of the sensing switch in extremely close proximity to the spreader frame, in the immediate region of its contact with the edge drive rolls, so as to be most highly and most reliably responsive to any tendency of dislodgement of the spreader frame with respect to the edge drive rolls. The system of the invention, provides for mounting of the sensing switch directly underneath the plane of the spreader frame, in order to maintain the area above such plane free of obstruction, while at the same time providing a system which is capable of reliable operation, day in and day out, in the relatively hostile conditions to which it is exposed.
More specifically, the system of the invention includes a magnetically actuated sensing switch, which is mounted on the supporting carriage for the edge drive roll, in a position to have its sensing element located directly under the plane of the roll and immediately adjacent the area in which the edge drive roll contacts the belt driving rolls of the spreader frame. Such a sensing element is provided at each side of the machine, so as to sense a tendency for dislodgement at either side. In conjunction with the magnetic sensing devices as thus described, the spreader frame itself includes, along each of its side rails, a magnetic element, which is mounted in the frame, between the support rolls and at a location as close as reasonably practicable to the adjacent edge drive roll, when the spreader is in its normal operating position. The arrangement is highly sensitive to any tendency toward dislodgement of the spreader frame, and serves to quickly shut down the equipment in response to any such tendency. In this respect, the system of the invention is operative to sense any displacement of the spreader frame independently of the amount or direction of accompanying lateral displacement of the edge drive rolls themselves, and thus is adapted to a significantly higher degree of sensitivity than has been attained heretofore.
In addition to being highly sensitive and responsive to malfunction, the system of the invention, even utilizing sensing devices mounted underneath the processing plane, is ideally suited for reliable, day-in-day-out operation in the rugged environment to which it is exposed. In this respect, the fabric passing over the spreader frame frequently may be wet with water or processing chemicals, to which the sensing elements may be directly exposed. Even where the fabric is processed dry, the presence of lint can be a problem with many control devices. However, inasmuch as the sensing elements are magnetically responsive, they may be easily completely sealed and thus not affected significantly by severe conditions of operation.
The system of the invention not only provides a significantly superior degree of operational effectiveness, but is also highly economical to install and maintain. Overall, it represents a highly advantageous improvement in the art.
For a better understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description and to the accompanying drawings.